1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for determining integrity of cement sections in wellbores.
2. Background of the Art
Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Modern wells can are drilled to great well depths, often more than 15,000 ft. Hydrocarbons are trapped in various zones in the subsurface formations at different wellbore depths. Such zones are referred to as reservoirs or hydrocarbon-bearing formations or production zones. A casing is generally placed inside the wellbore and the space between the casing and the wellbore (annulus) is filled with cement. A production string or assembly containing a number of devices is placed inside the casing to perform a variety of operations downhole, including, but not limited to, fracturing, treatment and production of fluids from the formation to the surface. Once the well is no longer productive, a section of the well is filled or plugged with cement and abandoned. It is important to determine the integrity of the cement section on an ongoing basis. Also, during the productive life of the wellbore and when it comes time to plug and abandon a well, it is desirable to determine the integrity of the cement between the casing and the wellbore.
The disclosure herein provides apparatus and methods for detecting leaks or breach through and around the cement sections in wellbores using nonradioactive tracers.